System for eliminating and removing hydrates and other blockages in undersea lines

ABSTRACT

The present invention addresses to a system for removing hydrates and other scales in subsea pipes in oil production fields. More specifically, the present invention addresses to a system for fighting and removing hydrates and other scales comprising independent traction modules, equipped with load cells that act by controlling other traction modules, wherein said traction modules are interconnected intercalated with armored cable sections. The system of the present invention is applied in rigid or flexible pipes that present restrictions or blocks to the flow.

FIELD OF THE INVENTION

The present invention addresses to a system for removing hydrates andother blocks in subsea pipes in oil production fields. Morespecifically, the present invention addresses to a system for fightingand removing hydrates and other blocks comprising independent tractionmodules, equipped with load cells that act by controlling the tractionmodules, wherein said traction modules are intercalatedly interconnectedwith sections of armored steel cable (steel cable with facilities forthe transport of electrical and/or hydraulic power, in addition to,optionally, a circuit for the circulation of fluids, aiming at makingenergy available for their locomotion, as well as the driving of toolsthat this may come to load). The system of the present invention isapplied in rigid or flexible tubes that present restrictions or blocksto the flow.

DESCRIPTION OF THE STATE OF THE ART

In the oil and gas exploration field, obstructions caused by hydrates orscales in subsea pipes are frequently observed. There are tools foraccessing and removing these obstructions, but they do not have greatreach, especially in the horizontal part of the tubes, since it onlyrelies on gravity for its positioning or limitations in relation toreach, due to friction between the cable and the wall of such tubes.

The formation of hydrate generates many losses for the exploration andproduction of oil and/or gas, restricting its flow rate and may evencause the obstruction of production or service lines. Researches and newdevelopments have emerged to minimize the loss of production in oilwells.

It is not possible to use hydrate inhibitors in production or servicelines after the block occurs, since hydraulic shims and columns ofliquids are formed that prevent the injection of these chemicals at thenecessary points. The hydrate formation is caused by high pressures andlow temperatures, typical conditions in oil wells at great depths.

Mechanical methods of scale removal are carried out through the use ofPIGs, but not all lines are “piggable”, requiring a specificconstructability of equipment and even the efficiency of these devicesis limited. There is still the possibility that the PIG will generate ablock if it drags a lot of material with the same. In addition, the useof PIG requires that there is flow for its displacement.

Another method used, the coiled tube, has difficulties due to the lowcapacity in relation to the reach, mainly in the horizontal part of theproduction tubes, since it only relies on gravity for its positioning.Some pieces of equipment with their own traction are used in wells, butthey are not suitable for pipes due to sharp bends, inflection pointsand the consequent friction, generating high loads to pull the powersupply cable, as well as the load on this cable for the recovery of thetraction device.

There are some systems that use two units, that is, a tractor module andan inspection module. As a rule, the tractor device is not driven toreturn, as it can “settle” when it “runs over” the cable that suppliesenergy thereto, increasing its entrapment inside the tube.

Pieces of equipment with its own means of locomotion are used, but theyare not suitable for tubes comprising sharp bends, inflection points andhigh friction caused by the power cables that these pieces of equipmentmake use of, providing high load to pull such a supply cable energy, aswell as high load on said cable at the time of equipment recovery, incase it is pulled back.

The tools currently used to fight hydrate and other obstructions are:

-   -   Coiled tubing—a tube positioned on a spool, and inserted from        the top of a riser, where it accesses the suspended section of        flexible or rigid tubes and wells in its vertical section and at        the beginning of the horizontalization curvature. This device        acts by gravity itself and the main limiting factor is the        buckling of this tube, due to its high slenderness.    -   Traction tools: used in the vertical, directional and horizontal        section of wells, typically structures with a large radius of        curvature, but without, or almost without, inflection points.

Document WO2008111844A1 refers to a steel cable tractor. Moreparticularly, it refers to a steel cable tractor comprising at least onedrive wheel positioned on a shifting mechanism connected to the steelcable tractor, in which the shifting mechanism is arranged so as tomaintain the drive wheel in a stressed manner against a well or tubewall. The shifting mechanism is at least rotatable or movable between afirst position, in which the drive wheel rests against the well wall onone side of the tractor, and a second position, in which the drive wheelrests against the well wall on the opposite side. In this sense, thesteel cable tractor applies a tension load that allows pulling the cablethat it carries, moving through the well. Steel cable tractors havetaken on considerable application in, for example, equipment andmaintenance work on oil wells. Many steel cable tractors are suppliedwith drive wheels that are tilting. Often the attached cable is used topull the steel cable tractor out of the well.

The invention PI0005931-3A addresses to an inspection PIG. These piecesof equipment designed for extensive lines are mainly used in subsea orunderground lines. The operating mechanism is through high pressurefluids that drive the PIG movement. The action of the pressure fluid ison the annular cup positioned either at the front or back part, and isresponsible for adjusting to the diameter of the piping and promoting acertain sealing. Accordingly, the fluid that drives the pig acts on theannular cup. Accordingly, moved by the flowing fluid, this mechanismcannot work well in clogged tubes.

Another type of PIG, based on a single body of polyurethane orfoam-based, and which are used in situations of lines with differentaccessories, are not sufficient for cleaning some types of scales,especially hydrates due to the hardness of the scaling.

Intermediate tractor devices are not adopted due to the difficulty insynchronism between such devices, among other reasons.

FIG. 10 shows an example of the coiled tubing system, which representsan embodiment of the state of the art, but which does not have a tractorat the end of the cable/rod/tube. This is only applicable in vertical orhorizontal sections with short reach, since the cable/rod/tube witheventual tools descends by gravity. However, the drawing alsoillustrates what the winch drum can be, which takes the armored cableintercalated with traction elements, proposed in this document.

Thus, there is currently no tool or means that is applied to the staticsection of pipes, especially the flexible ones that have moreaccentuated curvature characteristics. Furthermore, the static sectionsare the most susceptible to problems that may require suchinterventions, positioning themselves on the seabed, typically far fromthe inlet end of such tools.

The present invention solves a problem that makes it impossible to movetractor devices in the reverse direction: this problem is the risk ofthe tractor overlapping the electrical supply and control cable to whichthe device is coupled. This is solved with a control system associatedwith measurements performed by load cells installed at the rear end ofthe tractor module (21), or at both ends, when applied to intermediatemodules (20). Assuring a minimum value of tension in each cell, thetraction modules can act in a synchronized way with the cableretraction, increasing or decreasing the forward or backward speed ofeach module, ensuring that the cable always remains tensioned.

BRIEF DESCRIPTION OF THE INVENTION

The present invention refers to a system for fighting and removinghydrates and other scales comprising independent traction modulesarranged in series, and each traction module is coupled to the nexttraction module by an armored cable segment.

The traction modules (tractors), modules responsible for pulling thecable segments, are capable of not only being boosters or acting fortraction, but also as if they were modules for measuring loads. In thisway, the values of stresses caused by axial loads in the cables are notcumulative in a single cable. Accordingly, it became possible toincrease the loading concentrated in a single module, and therefore,making it more effective to reach the points of interest for scaleremoval.

This has an advantage over traditional PIGs and other technologies, aslarge tensile loads are not required in cables or systems that usebooster fluids with very high pressures. In addition, the cable thatinterconnects the tractor system contains within the same an umbilicalfor electrical and hydraulic supply, fluid circulation and cables forcollecting information from sensors.

BRIEF DESCRIPTION OF DRAWINGS

The present invention will be described in more detail below withreference to the attached drawings, which in a non-limiting way of theinventive scope, represent a preferred embodiment. Thus, there are:

FIG. 1 illustrates the system of the present invention positioned withina flexible tube, with a reach associated with the number of usedsegments;

FIG. 2 illustrates a top view of the socket for interconnecting betweenarmored cable segments of the present invention;

FIG. 3 illustrates a side view of the socket for interconnecting betweenarmored cable segments of the present invention;

FIG. 4 illustrates a side view of the rolling wheel used in the couplingbetween sockets of the present invention;

FIG. 5 illustrates a top view of the connection between two sockets thatinterconnect two sections of armored cable comprising a rollingaccording to the present invention;

FIG. 6 illustrates a side view of the connection between two socketscomprising a rolling according to the present invention;

FIG. 7 illustrates the angle lag that must ensure that rolling wheelstouch the inner surface of the tube, ensuring a reduction in theobserved friction;

FIG. 8 illustrates a side view of an alternative configuration to theuse of wheels with sockets shown in FIGS. 2 to 6 , where the set ofwheels snap together and are attached to the armored cable, in a splitsystem;

FIG. 9 illustrates a top view of an alternative configuration, using thewheels, in the split system;

FIG. 10 illustrates the conventional configuration, using the coiledtubing, a technology that is limited to wells or applications with shortreach.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a system for fighting and removinghydrates comprising independent traction modules (20), arranged inseries, and each traction module (20) is coupled to another nexttraction module (20), by an armored cable segment (10), in addition tothe end traction module (21) located at the end of the assembly.

The traction modules (20) and end traction module (21) of the presentinvention, also known as tractors, are preferably of the active type,that is, they comprise means of auto-locomotion, with electric orhydraulic drive. Furthermore, the traction module located at the end(21) comprises means for positioning tools to fight and remove hydratesand other blocks such as scale deposition. Further, the traction modules(20) are equipped with load cells that comprise the electronic devices,and sensors whose function is to control and supply the traction (20)and the end (21) modules.

The armored cable segments (10) are provided with tubings for thetransport of fluids (hydraulic and chemical products) along theirlength, as well as an electrical supply containing a plurality ofconductor wires and for data transport, in the same way as the traction(20) and end (21) modules themselves, which allows the (electrical andhydraulic) transmission to the next segment.

The armored cable segments (10) have, in their core, a layer containinga plurality of steel cables to meet the mechanical traction.Furthermore, the armored cable segments (10) comprise an outer sheath,preferably of nylon or Teflon, and comprise a preferred length of up tofive hundred meters; however, this length may vary due to differentconditions, such as the friction force per meter for a typical tubeconfiguration, internal diameter, internal material and geometry, radiiof curvature, average number of inflection points per km, and totaldistance to be reached.

The tractors or also traction modules (20) are intercalatedlyinterconnected with sections consisting of segments of steel armoredcable (10), and are further associated with the steel cable winch (30),so that the loads are always of tension, preventing damage to the set ofarmored cables (10) and traction modules (20).

The armored cable segments (10), according to the present invention,provide distances comprising approximately between 2 and 20 meters inlength (not limited to that), where, preferably, each segment comprises2 to 20 meters of cable, and are coupled to the other segments throughsockets (12) attached at their ends, as shown in FIGS. 2 and 3 .

FIGS. 3 and 5 show the sockets (12), which are structures comprising a“U”-shaped support, comprising two legs (13) with a hole (15) in eachleg (13) of the “U”. The coupling between two sockets comprisespositioning the sockets (12) so that each leg (13) of one socket (12) isbetween the two legs (13) of the other socket (12). The coupling furthercomprises the introduction of a rolling wheel (14), according to (FIG. 4), comprising a hole (16), so that the holes (15) of all the legs (13)of the two sockets (12), plus the hole (16) of the wheel (14) arealigned. The coupling between two sockets further comprises theintroduction of a locking pin (17) in the holes of the sockets (12) andthe wheel (14), functioning as a pivot axle between the sockets and anaxle for the wheel (14).

The sockets (12) of both ends of a sub-segment of the segment (10) and,consequently, the wheels (14) must have a relative positioning withmisalignment, or lag, of about 45° or about of 90° to each other, asshown in FIG. 7 . This lag allows the armored cable segment (10) not tosettle in such a way as to impair the operation of said rolling (14).

Each socket (12) must have (hydraulic and chemical) fluid andelectricity transmission facility, of the swivel type, in the same wayas between the socket (12) of the end of the armored cable segment (10)that connects to the traction module (20).

The armored cable segments (10), between a traction module (20) andanother, can reach lengths of up to 500 meters; therefore, the sockets(12) must resist high traction tensions. In this way, they arepreferably made of a material with sufficient strength to support theweight of at least three kilometers of such a set of cables. Saidsockets (12) provide the connection between the armored cable segments(10) and a rolling (14), using locking pins and nuts. The sockets (12)at both ends must have a misalignment, or offset, of about 45° or aboutof 90°, depending on the diameter of the rolling (14) and the length ofeach sub-segment. This lag allows the armored cable segment (10) not tosettle in a way that harms the operation of said rolling (14).

Additionally, the armored cable segments (10) can comprise steel wiresin different assembly directions, thus preventing twists from causingsaid settling of the armored cable (10), even with the use of saidsocket lag (12).

Alternatively, the need for sockets (12) with the aforementionedrelative positions can be replaced by the alternative configuration,shown in FIGS. 8 and 9 , that is, an alternative configurationconsisting of split devices (22) provided with rolling wheels (24). Suchdevices comprise a split structure, which grips the armored cable (10),avoiding the need for sub-segmentation of said cable. In this case,there are no sub-segments, there is only one pair of sockets (12), oneat each end of each armored cable segment (10), these maintaining theneed of having swivels in each of the sockets (12) , to perform theinterface between each end of the armored cable segment (10) and itsrespective module (20).

This split device (22) is secured by screws and nuts (23) on each sideof the axle of the rolling wheels (24), containing two wheels on thesame axle. There is no coupling between sub-segments, since there are nodiscontinuities in the armored cable segment (10). The distance betweeneach of the split devices (22), in this case, can be adjusted as afunction of the expected loads related to friction.

The present invention further enables the use of tractor devices of thestate of the art, as long as they undergo miniaturization, in order toallow their use in subsea flexible tubes, passing in more severe radiiof curvature, incorporating great value and flexibility of use to thesepieces of equipment. FIG. 10 shows an example of the coiled tubingsystem, which represents an embodiment of the state of the art, butwhich does not have a tractor at the end of the cable. This is onlyapplicable in vertical or horizontal sections with short reach, sincethe cable with eventual tools descends by gravity. In the same figure,there is a structure that represents a device that isolates the interiorof the tube from the external environment, acting as a BOP—Blow OutPreventor (40) and that needs to be adapted to the passage of thetraction tool (each of its segments), in addition to the wheel devices.

The BOP (40), typically used in drilling and well intervention, musthave shear gate valves, so that they allow the cable to be cut, in casethis is necessary to avoid uncontrolled fluid return.

The same must also be able to divert such flow, if any, to a safe place(vessel, vent, etc.).

The present invention solves a problem that makes it impossible to movetractor devices in the reverse direction; this problem is the risk ofthe tractor “running over” the electrical supply and control cable towhich the device is coupled. This is solved with a control systemassociated with load cell measurements installed at the rear end of themost advanced tractor module, or at both ends, when applied tointermediate modules. Assuring a minimum value of traction in each cell,the traction modules can act synchronously both in the advance and inthe retraction of the cable.

The system according to the present invention minimizes the problem offriction present in the solutions of the state of the art using armoredsteel cable—steel cable containing hydraulic hose and/or electric cableto feed the traction equipment and coupled accessories, at the same timethat allows the segmentation of the cable so that it can be pulled byseveral modules that, activated synchronously, divide the loadsgenerated by the friction between the cable and the internal walls ofthe tube.

The application according to the present invention is directed to rigidor flexible tubes that present restrictions or blocks to the flow, fortheir clearing.

The associated use of distributed controlled traction and frictionreducers in the armored cables (10) reduces the loads to tolerablelevels, allowing a reach of several kilometers from the platform wherethe tube is interconnected. With this, it is possible to fight blockscaused by hydrate formation or deposition of scales, allowing tools toaccess the pipe at points with such blocks or restrictions, said toolsconsisting of, for example, pieces of equipment for mechanical removal,application/circulation of chemicals, local heating generation, etc.,coupled to the module positioned at the end of the first cable segment.

With the reduction of scaling, there will be a reduction in the headloss to the flow during the production of wells, increasing theirproduction potential and, in the case of hydrates, which usuallyrestrict production completely, the return to production in much lesstime, when compared to conventionally adopted methodologies, forexample, the use of probes associated with the depressurization of thepipe.

The active intervention (enabled with the invention, for long distances)tends to accelerate the solution of the problem, not being limited topassive solutions (typically adopted with the use of interventionprobes), where one literally waits for the “ice to melt”.

Thus, with the use of the system object of the present invention, anorder of magnitude as to savings of approximately 90% is estimated,justifying its prompt adoption.

It should be noted that, although the present invention has beendescribed in relation to the attached drawings, it may undergo slightchanges, but not departing from the presented embodiment.

1- A SYSTEM FOR FIGHTING AND REMOVING HYDRATES AND OTHER BLOCKS,characterized in that it comprises independent traction modules (20)arranged in series, and each traction module (20) is coupled to the nexttraction module (20) by an armored cable segment (10), sockets (12) or asplit device (22); and a BOP device (40). 2- THE SYSTEM FOR FIGHTING ANDREMOVING HYDRATES AND OTHER BLOCKS according to claim 1, characterizedin that the traction modules (20) and the end (21) comprises means ofauto-locomotion that are electrically or hydraulically driven. 3- THESYSTEM FOR FIGHTING AND REMOVING HYDRATES AND OTHER BLOCKS according toclaim 1, characterized in that the traction modules comprise means forpositioning tools to fight and remove hydrates and deposition of scales.4- THE SYSTEM FOR FIGHTING AND REMOVING HYDRATES AND OTHER BLOCKSaccording to claim 1, characterized in that the means for positioninghydrate fighting tools is located in the end traction module (21). 5-THE SYSTEM FOR FIGHTING AND REMOVING HYDRATES AND OTHER BLOCKS accordingto claim 1, characterized in that the traction (20) and end (21) modulesare equipped with load cells that comprise the electronic devices andsensors. 6- THE SYSTEM FOR FIGHTING AND REMOVING HYDRATES AND OTHERBLOCKS according to claim 1, characterized in that the armored cablesegments (10) comprise segments preferably comprising 20 meters inlength, but not limited to this length, and are provided with means forthe transport of fluids, power supply and data transport along itslength. 7- THE SYSTEM FOR FIGHTING AND REMOVING HYDRATES AND OTHERBLOCKS according to claim 1, characterized in that the armored cablesegments (10) preferably comprise nylon or Teflon coating; and may reach500 meters between each traction module (20) or (20) and (21). 8- THESYSTEM FOR FIGHTING AND REMOVING HYDRATES AND OTHER BLOCKS according toclaim 7, characterized in that the segments comprise sockets (12) attheir ends for coupling between each segment. 9- THE SYSTEM FOR FIGHTINGAND REMOVING HYDRATES AND OTHER BLOCKS according to claim 8,characterized in that the sockets (12) comprise a “U”-shape support,comprising two legs (13) with a hole (15) in each leg (13) of the “U”.10- THE SYSTEM FOR FIGHTING AND REMOVING HYDRATES AND OTHER BLOCKSaccording to claim 9, characterized in that the coupling between armoredcable segments (10) comprises the positioning of the sockets (12) sothat each leg (13) of a socket (12) is located between the two legs (13)of the other socket (12), which will have channels forming a “swivel”rotating link that will allow the transmission of hydraulic pressure andelectrical signals. 11- THE SYSTEM FOR FIGHTING AND REMOVING HYDRATESAND OTHER BLOCKS according to claim 10, characterized in that thecoupling between armored cable segments (10) comprises the introductionof a rolling wheel (14) comprising a hole (16), of so that the holes(15) of all the legs (13) of the two sockets (12) plus the hole (16) ofthe wheel (14) are aligned. 12- THE SYSTEM FOR FIGHTING AND REMOVINGHYDRATES AND OTHER BLOCKS according to claim 11, characterized in thatthe coupling between armored cable segments (10) comprises theintroduction of a locking pin (17) in the holes (15) of the sockets (12)and in the holes (16) of the wheel (14), functioning as a pivot axlebetween the sockets and an axle for the wheel (14). 13- THE SYSTEM FORFIGHTING AND REMOVING HYDRATES AND OTHER BLOCKS according to claim 12,characterized in that the sockets (12) of both ends of a sub-segment ofeach armored cable segment (10) have an angle of 90° between suchsockets and their subsequent socket. 14- THE SYSTEM FOR FIGHTING ANDREMOVING HYDRATES AND OTHER BLOCKS according to claims 1 to 7,characterized in that the split device (22) has the cylindrical bodyadjustable to the armored cable (10) and with a locking system by screwsand nuts (23). 15- THE SYSTEM FOR FIGHTING AND REMOVING HYDRATES ANDOTHER BLOCKS according to claim 14, characterized in that the splitdevice (22) contains at least 2 wheels interconnected to the same axle.16- THE SYSTEM FOR FIGHTING AND REMOVING HYDRATES AND OTHER BLOCKSaccording to claim 15, characterized in that the sockets (12) or thesplit devices (22) are arranged in a misaligned manner in relation toeach other at any angle, preferably at the angles of 45° or 90°. 17- THESYSTEM FOR FIGHTING AND REMOVING HYDRATES AND OTHER BLOCKS according toclaims 1 to 16, characterized in that there is an electronic speedcontrol system of the wheels present in the traction (20) and the end(21) modules in order to ensure the existence of traction loads in thearmored cable segments (10).